Shimano Zee and Surly Marge Lite offset for Pugsley fat bike frame
Post date: Nov 29, 2013 7:16:55 AM
If you're not familiar with the Pugsley, it has track style dropouts AND a derailleur hanger. As I wanted to experiment with a single speed fat bike, the ability to easily switch between gears and SS pushed me to the Pugsley.
So how do I use the Surly offset wheelbuilding tool with my 10mm thru bolt hub? I'm a big fan of Roger Musson's excellent wheelbuilding book and it includes instructions on page 18. Just as Roger describes, the Surly spacer is 35mm long, or two times the Pugsley offset of 17.5mm.
Continuing with the convertible drivetrain theme, I selected the Shimano Zee hub for it's steel freehub body and 10mm thru bolt capabilty. I selected Wheelsmith DB14 spokes and Wheelsmith brass nipples for this wheel. The corrosion resistance offered by the brass nipples should help minimize the harmful affects of road salt that this bike is sure to encounter during winter riding. My friends at Wheel Fanatyk offer Wheelsmith products at great prices.
Proof that I was over thinking this offset build, Roger provided this elegantly simple solution for checking dish. Hold the spacer in place on the axle face and measure as normal. There's no need to have the tool in the truing stand during tensioning.
The Surley Marge Lite rim has two rows of thirty-two spoke holes to accommodate offset lacing. As seen above, lacing the wheel with all the spokes in line offsets the rim and tire to the non-drive side and creates chain clearance around the fat tire. Surly has detailed lacing instructions on their website. For a symmetrical wheel, you would lace side-to-side using alternating spoke holes. Click here to see my symmetrically laced front wheel.
I built a truing stand from the plans in Roger's book. As he demonstrates on page 45, you can use a standard quick release to hold the wheel as you are tensioning the wheel.
Maybe you've read this far and you're wondering if there are allowances for offset when calculating spoke lengths? The answer is yes. I tried to simplify the method I used in this short tutorial. For you engineering types, please forgive me for not including the mathematical explanation.
Once you've got the spoke lengths and offset lacing figured out, Roger's standard wheelbuilding procedure applies.
Regarding spoke tension, these rims are thick and over built in my opinion. As the spokes approach final tension, there is different feedback through the spoke wrench than with a standard mountain bike wheel. Based on this feel, I ended up with a final tension slightly less than I would use with a standard mountain bike wheel. Sorry, I can't offer a scientific explanation regarding this "feel". It's something I've developed from experience. Here is the (mostly) finished complete bike, now for some snow!!
I really like these DT Swiss 10mm thru bolts for the stiffness they add to the rear triangle and the extra bit of clamping pressure they offer that you can't get from a standard quick release.